Process of making cement.



R. C. NEWHOUSE.

PROCESS 0F MAKING CEMENT.

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1 ,1 84,656. Patented Muy 23, 1916.

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BAY C.

NEWHOUSE, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO ALLIS-CHALMERS MANUFACTURING COMPANY, OF MILWAUKEE, WISCONSIN, A CQRPORATION OF DELAWARE.

PROCESS OF MAKING CEMENT.

Specification of Lettera Patent.

Patented May 23, 1916.

Application tiled August 3l, 1914. Serial N 0. 859,929.

To all 'whom it may concern:

Be it known that I RAY C. Nnwnousa a citizen of the United States, resdin at Milwaukee, in the county of Milwau ee and State of Wisconsin, ha\'e invented a certain new and useful Improvement in Processes of Making Cement, of which the following is a speci cation.

This invention generally relates to )rocesses of making cement, particularly lortland cement, the preparation of which involves grinding prior to burning.

In the manufacture of Portland cement the most usual' process heretofore has been the dry process, in which the cement making materials are ground dry, burnt and then reground into cement.

Another process in use, but not so largely, is the wet process, in which the material is ground wet by insuring the presence of water sufiicient to form a slurry. This is donc either by adding water to the cement forming materials or in permitting the same to remain therein when Preliminarily resent as in the case of mar After grin ing in the form of slurry, the cement making materials are fed in their moist condition to the kiln and the moisture is first evaporated directly therein and then the materials are burnt to clinker after which they are ground direct to cement.

Tube mills are generally used for fine grinding and it is necessary in such mills to so regulate and restrict the feed thereto, that the product is within the prescribed limits of fineness required. These limits of fineness of the cement making materials ireliminnry to burning are defined by the imiting requirements of the kiln, these being that the particles of material must not be so coarse as to require too much time in fusin by the available heat, otherwise the wi pass through the kiln uiiburnt. If t e required tiine be allowed, then the heat to which the materials are subjected would be .so great as to form clinker much harder to grind. Too muclr coarse material could not therefore be permitted to pass from the tube mill with the predominant fine material,

necessitating restriction of the feed to the tube mill as stated. If the cement making materials fed to the kiln are of uniformly line grade, it follows that the product may be passed through the kiln at a greater rate than if the materials were finer and coarser than that grade, and that the finer this uniform product, the less time will be required to burn the same to clinker.

The capacity oi a tubo mill is reduced about 50 per cent. in order to vary the finenoss of the product from percent. passing a mesh screen, to 95 per cent. )assnlr such a screen. The ellieiency of a tullio mill will therefore be greatly increased by separating the oversize from its product and returning same to be recround. No restriction of the regulation otpthe feed to the tube mill will then be necessary. The ellicieney of a tube mill will also he greatly increased by separating from the feed thereto, imiteruil made line enough for the kiln in the pre liminary grinder.

Separating finely ground product is a difficult matter. For instance, either wet or dry material ma be easily Separated in a 20 mesh screen, ut this becomes impracticable when the material is to be separated by a Screen of from 100 to 200 mesh.

The separating out of material above 200 mesh is much more desirable on the raw side of the mill in order to attain a more perfect fusion or burning in the kiln. There is no advantage in havin a large proportion of 50() mesh material iigit contains much that is coarser than 100 mesh. This is because the burning of this material, which must be completely effected, will be that re uired for the coarse material so that all o the line material must be subjected to the heat required for the coarse. lf the coarse had been separated out, less heat would have been necessary to completely burn the remaining fine material. This is not true on the clinker grinding side of the mill where it is only necessary in order to give value to the cement, that its siin(l-e.iiii' iiir T capacity nuiv be large, that is, that there ie a maximum number of articles present. lt is not objectionable iere that some of these particles` are comparatively large.

The object of this invention is therefore to secure more eilicient production of cement.. lhe attainment of this object is brought about mainly by the separation of the cement making materials before enterlug the fine grinder or tube mill, making it, umieeeasary to load the tube mill with material already llue enough; also by the sep.

aration of the cement forming materials on emerging from the fine grinder or tube inill,. sending back the oversize to be reground, making it possible to feed to the mill at a greater rate. The se )arations referred to are preferably ma e hydraulically, for instance by means of classifiers. In this way an excess of water is present and for this reason the object of the invention is secondarily brought about -thereby increasing the efficiency of the finegrinder.

In the Wet rocess of making cement, referred t'o hereinabove, the water which was present or added to 'form a slurry was 'only suflicient for that purpose, that is to give the material a consistency making it possible to fee'd same. This was a's much sometimes as 50 per cent., and while with crystalline rocks it ran as low as 35 per cent., yet it was mainly a more expensive process than the dry process because f the presence of this excessive water, because more fuel had to be used in order to evaporate this nioi'sture. No attempt whatever was made to reduce the moisture content of the tube mill product before passing same tothe kiln. y

The specific objects 'of this invention are,to avoid passing through the fine grinder, the fines from the preliminary rinder, by preliminarily se arating. To increase the capacity of the ne grinder by increasing the eed to a maximum, the oversize being separated and returned. To maintain the "resence of sufficient water for greatest grim ing capacity. To reduce to a minimum the water content of the slurry before passing to the kiln. To increase the kiln capacity by feeding thereto a more uniform size o f cement making material. To save fuel. These and other objects will be apparent from the disclosure in the accompanying s )ecifieation and drawing illustrating modi ications of this invention.

The figures of the drawing schematically illustrate the steps of modified processes, the subject of this invention.

Referring particularly to Fig. 1, cement making materials are fed with excess of water to any form of coarse grinder, the product of which is then sent to a closed circuit including a separator and a fine frinder. The introduction of the product into the circuit is directly following the fine grinding ste i, so that the roduct from the coarse griner mixes witi that from the fine grinder, the mixture passing to the separator which preferably is a classifier. The oversize removed bythe separator passes along the closed circuit to the fine grinder, water being added thereto. The fines come from the separator in a wet condition and pass to a 4d'eliydr'ater such as a settling tank, whereby water is removed. The thickened product from the dehydruter is then passed to a kiln wherein it is burnt to clinker. The clinkcr then passes to the grinder wherein it is ground to cement.

It will be observed that in both the coarse and the fine grinder there is sufficient water present for maximum capacity grinding conditions. It will also be observedA that the separator removes the fines produced in the coarse Grinder before passing to the line grinder. it win ais@ be observed am the fine grinder may be operated to fullest capacity because the oversize therefrom is returned theretohy the separator to be re- 'r'oiuid. It will also be observed that the lines frk'iin'tl'ie'fin'e grinder are dehydrated before passing to the kiln. ll of these features assist in operating the machinery at its fullest capacity and with least wear and fuel required in burning the ceir'ie'nt making materials to clinker.

Referring to the modification shown in Fig. 2, this is in all respects the same as that of Fig. 1 with tivo exceptions; first, that the product from the coarse grinder enters the closed circuit vpreceding the fine 'grinding step, lrather than following same; and second, no water is introduced preceding the fine grinding step because the material from the coarse grinder has sufficient water therein.

The modification shown in Fig. 1 isl generally preferable over that shown in Fig. 2 because the fine material from the coarse grinder need not pass through the fine grinder. l

Referring to the modification shown in Fig. 3, this is 'the same in all respects as that shown in Fig. 1, with the exce )tion that a preliminary separator is introduced following the coarse grinder, the oversize being returned to the coarse grinder and thus forming a preliminary closed circuit including a coarse grinder and a separator. l Referring to the modificationyshown in Fig. 4, this is in all respects similar to that of Fig. 2, with the 'exception that it includes the same conditions as is present in the modification of Fig. 3 over that of Fig. 1. y

The addition of the separator following the coarse grinder in the modifications shown in Figs. 3 and 4, is for the purpose of assigning to the coarse grinder some of the work of grinding that would otherwise be performed in the fine grinder.

Referring to the modification shown in Fig. 5 the coarse grinding step and the fine grinding step are combined in a single mill. This is therefore much like the modification shown in Fig. 2, eliminating the coarse.

grinder and doing this Work, as well as the lino grinding, in the one mill.

Referring to the modification shown in Fig. 6, this is like the modification shown in Fig. 1, except that the. product of the fine grinder is passed on to the dehydrater instead of bein sent back to the separator. In other wor s, the product from the fine grinding ste is not separated.

The modi cation shown in Fig. 7 is similar to that of Fig. 6, except for the location of the dehydrater. Here the dehydrater serves to remove the water from the finos separated out by the classifier only, instead of as in Fi". 6 removin the water from the combinetd product o tho fine grinder and the fines separated out. The advanta e of the modification shown in Fig. 7 over t iat shown in Fig. 6 is in requiring a minimum of dehydratmg machinlhe advantage of the modifications shown in Figs. (i and 7 is that the separator handles the material but once.

lt should be understood that it is not desired to be limited to the exact details of the process disclosed, for obvious modifications will occur to a person skilled in the art.

It is claimed and desired to secure by Letters Patent,-

1. The process of making cement comprising, grinding cement forming materials with excess of water present, removin water from the ground material, directly urniug and grin in".

2. The process of making cement comprising, grindinf1r cement forming materials with excess o? water resent, separating out the fines, grinding t e oversize, removin water from the fines, directly burning and grinding, the material of said oversize bemg added to said materials prior to burning.

3. The process of making cement comprising, grindin cement forming materials with excess o water resent, separating out the fines, grinding tie oversize, removin water from the fines, directly burning an Qoplel of this patent may be obtained for ave cents cach,

grinding, the material of said oversize being added to said materials prior to separating.

4. The process of makmg cement comprising, grinding cement forming materials with excess of water present, adding other cement forming materials to the ground product, separating out the fines from the combined materials, grinding the oversize to form said other cement forming materials, removing water from the lines, directly burning and grinding.

5. The process of making cement comprising'coarse grinding cement forming materials with excess of water present, separatin out the fines, adding the oversize to the sai cement forming materials to be round therewith, subjecting the separated mes to a series of steps comprising, separating out the fines, grinding the oversize with excess of water present, removing water from the fines, burning and grinding, the material of said second oversize being added to said fines first se arated.

6. T ie process of making cement comprising, coarse grinding cement forming materials with excess of water present, separating out the fines, adding the oversize, to the said cement forming materials to be ground therewith, adding ground material to the separated fines, separating out the fines from the combined materials, returning and grindin the oversize to.form the ground materialg added, removing water from the fines, burning and grinding.

In testimony whereof, the signature of the inventor is afiixed hereto in the presence of two witnesses.

RAY NEWHOUSE. lVitnesses:

G. F. Dn WEIN, N. M. GUM/mn.

by addressing the Commissioner ot Patents,

Washington, D. 0. 

